TORONTO — The Egg McMuffin gave a mighty boost to fourth-quarter sales and earnings at McDonald’s Corp. after the classic fast-food chain debuted all-day breakfast at its U.S. restaurants.

The breakfast strategy, which began in October as part of the company’s effort to revive sales and answering a longstanding consumer demand, helped the chain realize its best quarterly growth in close to four years Monday.

Same-store sales, the volume at locations open for a year or more, leapt 5.7 per cent at the company’s U.S. restaurants, more than double the analyst forecast of 2.7 per cent.

But improving the U.S. business, the largest segment in the company is “fundamental” to the company’s turnaround strategy,” Steve Easterbrook, McDonald’s CEO, told investors on a conference call.

All-day breakfast was a big factor behind the quarterly boost, exceeding internal company expectations for the period and driving incremental sales, he said.

“Many customers who would have otherwise gone elsewhere are coming to McDonald’s to enjoy some of their favourite breakfast items at lunch, and through the rest of the day,” the CEO said. “All-day breakfast positions us to regain the market share we have given up in recent years.”

McDonald’s has been working to maintain its relevance in a market teeming with newer fast-food or “fast casual” rivals featuring more customizable food dishes, from Chipotle to Five Guys Burgers and Fries.

Prior to introducing all-day breakfast in the U.S., Easterbrook, who took the helm as CEO last March, began to simplify the menu and worked to speed up service at the world’s biggest restaurant chain and develop a leaner organizational structure.

“In the U.S., it will take at least six more months of positive comparable sales and guest count growth to progress through the sustained and prolonged growth phases of our turnaround,” Easterbrook said. “I am confident in the actions we are taking, and traction is beginning to take hold. Most importantly customers are noticing a difference,” with customer feedback scoring higher on the metrics of food quality, order accuracy, speed and friendliness.

Monday’s results signalled the second quarter in a row of positive results in its home market of the U.S., where same-store sales grew 0.9 per cent in the third quarter after seven straight quarters of declines.

Earnings were US$1.28 a share, excluding items, compared with analyst forecasts of US$1.23.

Revenue was US$6.34 billion in the period, a decline of 4 per cent but a rise of 5 per cent in constant currencies, beating analyst estimates of US$6.23 billion.

Same-store sales in its leading international markets rose 4.2 per cent in the period amid strong results in the U.K., Canada and Australia. Canada is second-highest in sales and guest count growth among McDonald’s 12 major global markets, behind Australia.

Operating income fell 5 per cent, or a rise of 8 per cent in constant currencies, thanks to higher franchise margins.